The tumor proteasome as a novel target for gold(III) complexes: implications for breast cancer therapy.

Although cisplatin plays a vital role in the treatment of several types of human cancer, its wide use is limited by the development of drug resistance and associated toxic side effects. Gold and gold complexes have been used to treat a wide range of ailments for many centuries. In recent years, the use of gold(III) complexes as an alternative to cisplatin treatment was proposed due to the similarities of gold and platinum. Gold(III) is isoelectronic with platinum(II) and gold(III) complexes have the same square-planar geometries as platinum(II) complexes, such as cisplatin. Although it was originally thought that gold(III) complexes might have the same molecular target as cisplatin, several lines of data indicated that proteins, rather than DNA, are targeted by gold complexes. We have recently evaluated cytotoxic and anti-cancer effects of several gold(III) dithiocarbamates against human breast cancer cells in vitro and in vivo. We have identified the tumor proteasome as an important target for gold(III) complexes and have shown that proteasome inhibition by gold(III) complexes is associated with apoptosis induction in breast cancer cells in vitro and in vivo. Furthermore, treatment of human breast tumor-bearing nude mice with a gold(III) dithiocarbamate complex was associated with tumor growth inhibition, supporting the significance of its potential development for breast cancer treatment.